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Nervous System
Chapter 12: Nervous system: Nervous Tissue
| Question | Answer |
|---|---|
| Describe the three general functions of the nervous system. | 1. Collect information 2. process and evaluate information 3. initiate response to information |
| Describe the structural components included in the CNS and those in the PNS. | Describe the structural components included in the CNS and those in the PNS. |
| Central nervous system | 1. Brain 2. Spinal cord |
| Peripheral nervous system | 1. Nerves 2. Ganglia |
| Explain he functional organization of the nervous system. | Explain he functional organization of the nervous system. |
| SENORY NERVOUS SYSTEM | detects stimuli and transmits information from receptors to the CNS. |
| Somatic Sensory | sensory input from the receptors of the five senses (ex: eyes) and proprioceptors. |
| Visceral Sensory | Sensory input from receptors of the internal organs (ex: heart) and blood vessels. |
| MOTOR NEROUS SYSTEM | initiates and transmits information from the CNS to effectors. |
| Somatic Motor | Motor output to skeletal muscle. |
| Autonomic Motor | Motor output to cardiac muscle, and gland. |
| Describe the structure of a nerve and explain how nerves are classified structurally and functionally. | Describe the structure of a nerve and explain how nerves are classified structurally and functionally. |
| Nerve | an organ composed of cablelike bundles of axon, connective tissue layers, and blood vessels, and it is a component of the peripheral nervous system. |
| Fascicle | within the nerve there are many axons are bundles into a structure called a fascicle. |
| Epineurium | a thick layer of dense irregular CT that encloses the nerve. It ensheathes the entire nerve to protect and support it. |
| Perineurium | a layer of dense irregular CT that wraps around each fascicle. |
| Endoneurium | is a delicate layer of areolar CT that surrounds each axon. |
| STRUCTURE | STRUCTURE |
| Cranial nerves | extend from the brain |
| Spinal nerves | extend from the spinal cord |
| FUNCTION | FUNCTION |
| Sensory Nerves | contain only neurons that relay information TOWARD the CNS (sensory neurons) |
| Motor nerves | contain neurons that relay information AWAY from the CNS (motor neurons) |
| Mixed nerves | contain both sensory and motor neurons. -Most named nerves are mixed nerves. -In mixed nerves an individual sensory or motor neurons still transmit only one type of information. |
| Compare and contrast nerves and ganglia. | Compare and contrast nerves and ganglia. |
| Nerves | bundles of AXONS within the PNS. |
| Ganglia | clusters of neuron CELL BODIES within the PNS. |
| List and explain the five distinguishing features common to all neurons. | List and explain the five distinguishing features common to all neurons. |
| Excitability | responsiveness to a stimulus |
| Conductivity | involves an electrical change that is quickly propagated along the plasma membrane as voltage-gated channels open sequentially during an action potential. |
| Secretion | neurons release neurotransmitters in response to conductive activity. |
| Extreme Longevity | most neurons formed during fetal development are still functional in very elderly individuals. |
| Amitotic | During fetal development most neurons lose their ability to form new cells through cell division. |
| Describe the anatomic features common to most neurons. | Describe the anatomic features common to most neurons. |
| Cell body (SOMA) | houses both the nucleus and the cytoplasm. |
| Perikaryon | Cytoplasm of the cell body |
| Dendrites | tend to be relatively short, small, tapering processes that branch off the cell body. -brings information to the cell body -the greater number of dendrites, the more input a neuron may receive. |
| Axon | longer process emanating from the cell body to make contact with other neuron, muscle cells, or gland. |
| Axoplasm | cytoplasm of the axon. |
| Axolemma | plasma membrane of an axon |
| Axon hillock | the axon emanating from the triangular, cone-shaped region of the cell body |
| Axon collaterals | the side branches to an axon. |
| Synaptic knob | extreme tips of the fine extensions. |
| Synaptic vesicle | within the synaptic knob and houses a neurotransmitter. |
| Myelin sheath | insulates the axons |
| neurofibril nodes | the uninsulated regions of the axon between the myelin sheaths. |
| cytoskeleton | the entire neuron has an extensive cytoskeleton which is composed of microtubules, microfilaments, and a type of intermediate filament is called NEUROFILAMENT. |
| neurofibrils | the neurofilaments aggregate to form parallel bundles. |
| Explain the difference between anterograde transport and retrograde transport. | Explain the difference between anterograde transport and retrograde transport. |
| Anterograde Transport | the movement of materials from the cell body toward synaptic knobs |
| Retrograde transport | is the movement of materials from the synaptic knob towards the cell body. |
| Distinguish between fast axonal transport and slow axonal transport and give examples of the different substances moved by each. | Distinguish between fast axonal transport and slow axonal transport and give examples of the different substances moved by each. |
| Fast axonal transport | -400 millimeters per day -involves movement along microtubules |
| Fast axonal transport substances moved | cellular structures in the cell body are moved anterograde transport & include vesicles organelles & glycoproteins required at the synapse used vesicles to be broken-down & recycled & potentially harmful agents are moved retrograde transport |
| Slow Axonal Transport | - 0.1-0.3 millimeters per day - this type of movement results from the flow of the axoplasm (axoplasmic flow.) |
| Slow Axonal Transport substance moved | -ONLY ANTERGRADE -these substances include enzymes, cytoskeletal components, and new axoplasm for regenerating axons. |
| Name and describe the four structural categories of neurons. | Name and describe the four structural categories of neurons. |
| Multipolar neuron | Multiple processes extend directly from the cell body; typically, many dendrites and one axon; most common type of neuron |
| Multipolar neuron EXAMPLES | ALL MOTOR NEURONS; MOST INTERNEURONS |
| Bipolar neuron | two processes extend directly from the cell body; one dendrite and one axon; relatively limited in where they are located |
| Bipolar neuron EXAMPLES | Some special sense neurons (ex: retina of the ye, olfactory epithelium in nose) |
| Unipolar neuron | Single short process extends directly from the cell and looks like a T as a result of two processes into one long axon. |
| Unipolar neuron EXAMPLES | most sensory neurons |
| Anaxonic neuron | processes are only dendrites, no axon present. NO ACTION POTENTIAL |
| Anaxonic neuron EXAMPLES | interneurons |
| Name and describe the three functional categories of neurons and where each is primarily located. | Name and describe the three functional categories of neurons and where each is primarily located. |
| Sensory neurons | the neurons of the sensory nervous system. They are responsible for conducting sensory input from both somatic and visceral sensory receptors. |
| Sensory Neurons LOCATION | -Some are unipolar -some are bipolar like in the retina of the eye and olfactory epithelium of the nose |
| Motor neurons | - the neurons of the motor nervous system, conducting motor output away from the CNS to both somatic effectors (skeletal muscle) and autonomic effectors (cardiac and smooth muscle and glands) -MULTIPOLAR |
| Interneurons | -lie entirely within the CNA -they recieve stimulation from many other neurons and carry out the integrative function of the nervous system- that is they receive, process, and store information - the decide how the body will respond to its stimuli |
| Interneurons LOCATION | -facilitate communication between sensory and motor neurons -99% of are neurons are this -MULTIPOLAR OR ANAXONIC |
| Define a synapse | the specific location where a neuron is functionally connected to either another neuron or effector (muscle/gland) |
| compare and contrast the structural and functional difference between a chemical synapse and an electrical synapse. | compare and contrast the structural and functional difference between a chemical synapse and an electrical synapse. |
| Chemical synapse MOST COMMON | -transmission is unidirectional -involves a presynaptic and postsynaptic neuron -involves a neurotransmitter EXCITABILITY- depolarize INHIBITORY- hyperpolarize -allow for variable signal intensities |
| Presynaptic neuron | which is the signal producer (releases neurotransmitter) |
| Postsynaptic neuron | the signal receiver, or target (binds neurotransmitter) |
| Electrical Synapses | -occurs between cell electricity coupled via GAP JUNCION -electrical current ions flow directly from axoplasm of one neuron to next -transmission is bidirectional -transmission is nearly instantaneous -in brain: programed for automatic behaviors. |
| Describe the structure and function of the four types of glial cells within the CNS and the two types of glial cells within the PNS. | Describe the structure and function of the four types of glial cells within the CNS and the two types of glial cells within the PNS. |
| Astrocytes | 1-helps form the blood-brain barrier 2- regulates interstitial fluid composition 3-provided structural support and organization to CNS 4-Assists with neuronal development 5-alters synaptic activity 6-replicates to occupy space of dying neurons |
| Ependymal cells | 1- lines ventricles of brain and central canal of spinal cord 2- assists in production and circulation of the CSF |
| Microglial cells | 1- phagocytizes substances in the CNS 2-Protects the CNS by engulfing infectious agents and other potentially harmful substances |
| Oligodendrocytes | 1- Myelinates and insulates CNS axons 2- Allows faster action potential propagation along axons in the CNA |
| Satellite cells | -physically separate cell bodies form their surrounding interstitial fluid -insulate the body -regulate the continuous exchange of nutrients and waste products between neuron cell bodies and environment |
| neurolemmocytes | -wrap around the insulate axons within the PNS to form a myelin Sheath. -allows for faster propagation of action potential |
| List the distinguishing features of glial cells. | List the distinguishing features of glial cells. |
| Glial cells (neuroglia cells) | -help neurons with their functions -cooperate to physically protect and help nourish neurons -provide an organized framework for developing neurons |
| Define myelination and describe the composition and function of a myelin sheath. | Define myelination and describe the composition and function of a myelin sheath. |
| Myelination | is the process by which park of an axon is wrapped with myelin. |
| Composition of myelin sheath | insulating covering around the axon that consists of repeating concentric layers of plasma membrane of glial cells -made from many lipids |
| function of a myelin sheath | -insulates and protect axon -allows the electrical impulses to travel quickly and efficiently between one nerve cell and the next. |
| Distinguish between the myelination process carried out by neurolemmocytes in the PNS and by oligodendrocytes in the CNS. | Distinguish between the myelination process carried out by neurolemmocytes in the PNS and by oligodendrocytes in the CNS. |
| PNS | -myelinate ONLY 1-milimeter portion of a SINGLE axon -takes many neurolemmocytes to myelinate the entire axon. -the gaps between the neurolemmocytes are NUEROFIBRL NODES. |
| CNS | -oligodendrocyte can myelinate 1-millimeter portion of several axons and just one -the cytoplasmic extensions of it wrap repeatedly around a portion of each axon where plasma membrane layers of the it forms the sheath -also have neurofibril nodes |
| List the factors that influence regeneration of PNS axons and explain why axon regeneration in the CNS is limited. | List the factors that influence regeneration of PNS axons and explain why axon regeneration in the CNS is limited. |
| factors that influence regeneration of PNS axons | 1- the amount of damage 2- the distance between the site of the damaged axon and the structure it innervates. |
| Why axon regeneration in the CNS is limited? | -oligodendrocytes do not release a nerve growth factor & inhibit axon growth by producing /secreting growth-inhibitory mol - there is a large number of axons -astrocytes and connective tissue cartilage forms scar tissue that obstructs axon regrowth. |
| Distinguish between a pump and a channel and describe the three specific states of a voltage-gated Na+ channel. | Distinguish between a pump and a channel and describe the three specific states of a voltage-gated Na+ channel. |
| Pumps | maintain specific concentration gradients by moving substances up (against) a concentration gradient, requires CELLULAR ENERGY. |
| Channels | provide the means for a substance to move down (with) its concentration gradient. |
| voltage-gated Na+ channel RESTING STATE | activation gate is closed, which prevents Na+ entry |
| voltage-gated Na+ channel ACTIVATION STATE | both the activation and inactivation gate are open (activation gate opens in response to a voltage change); Na+ moves into the cell through the open channel |
| voltage-gated Na+ channel INACTIVATION STATE | inactivation gate is closed, which prevents Na+ entry |
| list the channels and pumps that are located along the entire neuron and identify the general function of each. | Na+ leak channels k+ leak channels na+/k+ pumps they maintain RMP |
| describe the four functional segments in a neuron, including the distribution of channels and pumps in each. | describe the four functional segments in a neuron, including the distribution of channels and pumps in each. |
| receptive segment | -dendrites and the cell body -chemically gated channels significant numbers of vi=oltage-gated channels are present -more Na+ moves into the cell than K+ |
| initial segment | -axon hillock -contains both voltage-gated Na+ channels and K+ |
| conductive segment | -axon and terminal extensions -contains both voltage-gated Na+ channels and K+ |
| transmissive segment | includes the synaptic knobs and contains both voltage-gated Ca2+ channels and Ca2+. |
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